It is said that there is no constitutional clause ensuring the freedom of speech to UK citizens. Despite that, the press in the UK and United States have similar freedoms.
How does the US contrast freedom of speech with illegality of certain words and ideas? How are certain ideas made illegal despite freedom of speech, for example holocaust denial, defamation, rude words, protection of legal information, of corporate secrets, etc.?
I don't know enough about the UK to give a complete, contrasting answer. I'll tell you about the US and hopefully someone else will give a better more complete answer later.
Generally, nothing is illegal to say in the US as long as it can be half argued to be an expression of ideas. You can literally walk into a courthouse with the words "fuck the draft" on your shirt, and it's perfectly legal. Cohen v California.
Even disgustingly dishonorable lies, when not perpetrated for the purpose of financial gain, are okay. US v Alvarez.
In fact, fake child pornography may be legal simply because it could fall into the category of art and art is considered speech since it is used to convey ideas. Ashcroft v Free Speech Coalition.
The restrictions come into play when you are not expressing ideas at all. For example libel and slander, lying to defraud people for financial gain, or obscenity with no speech content.
Health and education information are legally protected and can't be disclosed without your consent. HIPAA is the law protecting health related privacy. I don't know the name of the law protecting education information. In general, privacy is protected because the value of privacy outweighs the value of the limited, if any, ideological content that could be conveyed.
Corporate secrets aren't directly protected by the government. One signs a contract with one's employers promising not to disclose secrets and the government only gets involved in civil court if one violates said contract.
Many of the things you list aren't actually illegal in the United States, at least not criminally. The first amendment is pretty explicit that the government can't make the exercise of speech illegal, though over time the Supreme Court has ruled that there are certain compelling situations that restricting speech is allowed. Generally exceptions tend to follow the same pattern that the state must provide a compelling reason/interest to restrict speech in a certain context.
you can find a more comprehensive list here.
UK has no freedom of speech. Their police force actively monitor Twitter for any offensive tweets. "Promoting racism and discrimination" is also an arrestable offense.
Of course, like all laws, this isn't equally applied to everyone. Some people are more equal than others, and can get away with it.
https://hequal.files.wordpress.com/2015/04/sarah-noble-kill-all-men-who-do-that.jpg?w=700
There is really no comparison. The UK has much less freedom of speech both in theory and in practice. Some examples: In the UK it is a criminal offence to deliberating offendinsult someone in public; there is both a government and a corporate list of websites no one is allowed to access which is enforced by the isps; some political groupings are "banned" if they are said to be linked to terrorism; spontaneous protests are illegal without police permission and so on and so forth.
It is also much easier to sue someone for libel in the UK and it is very expensive to defend yourself even if you end up winning the case.
I don't know if there are any examples of where the UK has freer speech than the US.
Freedom of speech is significantly but not drastically less protected in the UK than in the US.
Please note that I am NOT a lawyer. What follows is merely info I picked up from a long term interest in freedom of speech issues, sharpened by once thinking I was going to be involved in a legal case.
Historically neither English (and I believe also Scottish) statute law nor Common Law gave any specific assertion of the principle to freedom of speech, except (and it is a big "except") in the sense that it was a principle of law that anything not specifically prohibited was permitted. In practice this allowed freedom of speech except where limited by laws against slander, libel, sedition, blasphemy, obscenity, disclosure of official secrets etc.
The situation changed somewhat when the UK acceded to the European Convention of Human Rights in 1951 and more strongly with the Human Rights Act 1998, which incorporated the European Convention on Human Rights into domestic law. Article 10 of the ECHR states that everyone has the right to freedom of expression.
A significant precedent under the ECHR was Handyside vs UK (1976), which specifically stated that ideas that offend, shock or disturb are protected. (Though Handyside still lost his case.)
The Human Rights Act / Article 10 of the European Convention on Human Rights are thus the closest the UK has to an equivalent to the First Amendment of the US Constitution.
The main Act of Parliament curtailing free speech in the UK is the Public Order Act 1986.
Part 3 of the Act makes it a criminal offence to use (Section 18) or publish (Section 19) threatening, abusive or insulting words or behaviour with the intent of stirring up racial hatred where racial hatred is likely to be stirred up.
In 1994 a new section 4A was added regarding harassment "which causes another to fear, on at least two occasions, that violence will be used against him or her; or causes another serious alarm or distress which has a substantial adverse effect on his or her usual day-to-day activities".
In 2006 a new section 3A was added extending it to cover religious hatred.
In 2008 section 3A was extended to cover hatred based on sexual orientation.
See this link to the Crown Prosecution Service for details: http://www.cps.gov.uk/legal/p_to_r/public_order_offences/
Holocaust denial is not illegal in the UK, nor are rude words.
Defamation law is much more harsh in the UK than the US.
Media Law by Robertson and Nicol (5th edition 2008) is a good reference source.
